1. Field of the Invention
This invention relates to an electrical connection device employing an anisotropic electrically conductive film.
2. Description of the Related Art
In keeping up with the reduction in size and thickness of electronic components, the circuitry used in the electronic components is increasing in density and in precision in design rule. Since the connection between the electronic components and the fine-sized electrodes cannot be coped with by the conventional solder or a rubber connector, an adhesive or a filmed article, exhibiting anisotropy and electrical conductivity, referred to below as a connecting member, is preferentially used in order to cope with the tendency towards fine pitch.
This connecting member is comprised of an adhesive, containing a pre-set amount of the electrically conductive material, such as electrically conductive particles. This connecting member is provided between protuberant electrodes of the electronic components and an electrically conductive pattern of a printed circuit board and is pressured with or without heating to interconnect the electrodes of the electronic components and the printed circuit board. Moreover, the neighboring electrodes are insulated from each other and the protuberant electrodes are bonded and secured to the electrically conductive patterns of the printed circuit board.
The anisotropic electrically conductive film is mainly used as an adhesive film for the peripheral portions of a liquid crystal panel. Recently, the anisotropic electrically conductive film has come to be used in the field of semiconductor mounting in which a LSI (large-sized integrated circuit) chip is directly mounted on a resin substrate such as a mother board.
With the anisotropic electrically conductive film, electrically conductive particles are captured between electrodes desired to be connected to each other for establishing electrical connection therebetween. In the electrical connecting portion in the vicinity of the conventional liquid crystal panel, a large number of electrically conductive particles contributing to electrical connection can be provided, because of the large electrode area, so that the connection resistance hardly presented problems.
Meanwhile, in flip-chip mounting, which has recently attracted attention, endeavours have been made to reduce the pitch and the area of the electrodes, due to reduction in size of the components. In the connection employing the anisotropic electrically conductive film, the number of captured particles is reduced with the reduction in size of the electrodes, thus raising the resistance value per electrode.
Heretofore, tens to hundreds of particles can be provided between the electrodes. In recent mounting configurations, the number of the particles is reduced to only a few.
That is, in recent mounting configurations, the number of the particles of the anisotropic electrically conductive film taking part in the electrical connection is only a few, it is necessary to reduce the connection resistance value by these few particles to raise the electrical connection efficiency.